1. Field of Invention
The present invention generally relates to the field of security tags, and more particularly, to a system and method for adding functionality to security tag readers.
2. Description of Related Art
Several references disclose receiving radio frequency signals at one frequency and retransmitting them at a different frequency. For example, U.S. Pat. No. 4,622,557, issued to Westerfield on Nov. 11, 1986, discloses reception, downconversion and retransmission of GPS satellite signals in a system for determining a splashdown location by sonobuoys. The sonobuoys receive the GPS satellite signals, and downconvert them to a baseband frequency using frequency multipliers and filters. A local oscillator and a frequency synthesizer are used to modulate the signal at the new transmit frequency. The modulated signals at the new transmit frequency are then transmitted to an aircraft.
U.S. Patent Publication No. 2009/0016260 A1 by Thesling discloses a gateway for receiving a radio frequency signal at one frequency and transmitting it on one of a plurality of different frequency channels based on priority determinations. U.S. Pat. Nos. 6,215,988 (Matero), 6,397,044 (Nash) and 7,162,218 (Axness) also disclose receiving and transmitting radio frequency signals at different frequencies. However, none of the foregoing references disclose a method for converting tag reader devices operating at one frequency into tag reader devices capable of operating at different frequencies.
Additionally, U.S. Pat. No. 6,075,972, issued on Jun. 13, 2000 to Laubach, discloses a CATV network having transmitter and receiver appliqué modules. The appliqué modules are added to the network to increase network functionality. A signal from a cable modem at the home of the user in the Laubach network is received from a cable modem at a first frequency by a transmitter appliqué. The transmitter appliqué upconverts the signal is to a second frequency. The transmitter appliqué then transmits the upconverted signal to a network headend controller. The transmitted signal is received by a receiver appliqué coupled to the headend controller. It is then downconverted to a third frequency, and applied to the headend controller by the receiver appliqué.
U.S. Pat. No. 6,362,738, issued to Vega on Mar. 26, 2002, teaches the use of a plurality of detector circuits operating at different frequencies to permit a tag reader to respond to either RFID tags or EAS tags. U.S. Pat. No. 7,359,672, issued to Lynch, discloses providing combined EAS and RFID functionality in a tag communication system. The Lynch system uses much of the same circuitry for multiplying, upconverting and downconverting radio frequency signals in a system for converting the signals to different frequencies. The frequency conversion disclosed by Lynch includes conversion between microwave and millimeter signals. U.S. Pat. No. 6,658,237, issued to Rozenblit on Dec. 2, 2003, discloses using a tunable local oscillator for producing multiple retransmission bands from a baseband signal. For example, the retransmission bands can be the different frequency bands assigned to different cells in a mobile telephone communication system, such as frequencies in the range of 890 Mhz to 960 MHz. U.S. Patent Publication No. 2009/0117938 A1, filed on Nov. 2, 2007 by Georgantas, discloses a system with a plurality of receive frequencies and a plurality of transmit frequencies. However, none of the foregoing references disclose a system or method for converting tag reader devices operating at one frequency into tag reader devices capable of operating at different frequencies.
Thus, there remains a need for a method for conveniently converting tag readers operating at one frequency into tag readers capable of operating at different frequencies.
All references cited herein are incorporated herein by reference in their entireties.